Air purifying method

ABSTRACT

The invention concerns a novel method for purifying air and gasses, consisting of an optimized air ventilation slab, with its air ventilation pipes, air ventilation pipettes and air diffusion plugs; optionally a complementary cellular material enabling the material to be supported providing biofiltration, purification or treatment of air, and optionally a device for diffusing liquids and/or bacteria and/or enzymes, allowing the biofilter to act as the equivalent of a gas scrubbing tower.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase filing under 35 U.S.C. §371 ofPCT/FR2005/002948 filed Nov. 28, 2005, which claims priority to FrenchPatent Application No. 0412698, filed Nov. 30, 2004. The entire contentsof each of the above-applications are incorporated herein by reference.

This present invention concerns the areas of composting, the eliminationof pollution, and the treatment of waste. Its main purpose is to improvecomposting processes and certain other processes associated with theelimination of pollution and the treatment of waste.

It is known that composting processes on an aeration bed improve thecomposting process and bring about a reduction in the length of thecomposting process. In this context, it is traditional to consider thatthe composting process is accelerated by virtue of the aeration bed, andthat it can be divided into three phases, namely a first phase, known asfermentation, which traditionally lasts for about four weeks, a secondphase, called maturation or secondary fermentation, which lasts for sixto eight weeks, and finally a phase known as refining, which can lastfrom several weeks to several months, with a view to refining theproduct and its commercialisation. It should be noted that thecommercialisation of composts can also take place from the end offermentation and or from the end of the maturation period, before it hasbeen refined.

After the fermentation phase, the compost produces is described as“fresh”.

After the maturation phase, the compost produced is described as“mature”.

In practice, if one wishes to produce a “mature” compost, it isnecessary to leave the compost to break down on the fermentation baseand then on the maturation base, which in all is at least 10 weeks oreven 12 weeks or longer, and to complete the aeration of the organicwaste on the fermentation base, or on both of these bases (fermentationand maturation) through the complementary turning of the waste, using amachine of the loader or spinner type, at least during the maturationperiod or even the fermentation period.

It is also known that, in the context of composting processes onaeration beds, composting solutions have already been developed withmaximum heap heights, recommended by the process inventors, of threemeters, for green waste and the fermentable waste or biowaste, andmaximum heap heights of two meters to two meters fifty for compostedsludges.

It is further known that composting processes have recently beenimproved by technological innovations concerning measurement of the gascontent in composting platforms (patent PCT FR 02 00039 dated 8 Jan.2002 and entitled “An optimised device for discontinuous regulation andmeasurement of the content of oxygen or any other gas, in platforms usedfor composting or the treatment of waste”).

It is further known that other improvements have also been made to thedesign of the aeration beds, in particular by the design of modulardevices and new clip systems for the design of aeration pipettes fittedto the main aeration pipes and installed in the aeration composting beds(patent PCT 03 01382 dated 2 May 2003 and entitled “Modulable andoptimised installation for the composting of organic materials”).

The composting installations of prior art, and those installed with thelast two technologies mentioned above, have different drawbacks whichwill be described in detail below.

Turning of the compost heaps is the standard technique in the area ofcomposting and the treatment of certain waste materials (stabilisationof the refuse, elimination of pollution from polluted soil and earth,etc.) since this allows one to ensure consistently even breakdown of theorganic material and purification of the latter in depth.

The recommended height of the compost heap on an aeration bednevertheless remains limited to three meters for green waste, biowasteand fermentable waste, and to two meters fifty for sludges. Above this,the breakdown of the organic material is poor, since it is uneven due tovariability of the air passages in the heaps.

The new technology of air sampling and measurement of the oxygen contenthas the drawback that it favours the appearance of condensation productsin the intake pipes for sampling of the gases in each heap. Over time,the gas-sampling pipe fills up with condensation products and alsoclogs, preventing measurement gases from being monitored. In certainwaste composting applications, the air drawn in from the sampling rodsinserted into each compost heap, for measurement of the oxygen,transports organic particles or fine materials in suspension, which areable to form a sticky substance in the gas measuring pipe, which canprevent operation of the solenoid valves that control sampling of thegases under investigation.

In the design of the new platforms for the composting or for thetreatment of certain waste materials, the distribution of air, andtherefore the associated aeration bed, becomes a central element of theprocess. The result is an improvement in the aeration potential and theeffectiveness of the base or bed, the flows in the latter, and even thedesign of the aeration pipes and the aeration pipettes associated withthem become an important factor. In this context, it has appeared to beuseful to make improvements to the design and the industrial manufactureof the aeration pipettes associated with the aeration bed.

It has become apparent that it is possible for the pipettes to becomeclogged at the head of each pipette, because of the waste present on theaeration bed, when this aeration bed is incorrectly constructed. This isthe case in particular when the pipette heads are located above the topscreed constituting the aeration bed, and not at the level of thelatter. It has also been observed that, despite the securing clips ofthe pipette heads, there is a risk that the aeration pipettes can easilybecome detached from the aeration pipes, thereby rendering the formationof the bed more difficult.

In the composting processes, in particular of sludge and biowaste, thecreation of a vacuum in the waste is the rule, and the need to deal withthe foul air leads to the construction in particular either ofbiofilters or of the scrubbing towers, to deal with the air inparticular, and also, though not exclusively, to deal with gases thatcontain ammoniac and/or sulphurs.

Regarding the biofilters, these are often equipped with a grating tosupport the biomass used to process the foul air. Certain manufacturersof composting systems have replaced the support grating by a ballast ofangular stones similar to those used to support of the rails of railwaylines (the ballast used by SNCF, the French national railway company).The sole function of this ballast is to support and holds the biomass,and/or to position the aeration pipes for distribution of the pollutedair under the biomass.

The objective of this present invention is to overcome the drawbacksmentioned above, and to improve the design and the effectiveness both ofthe aeration bed and, in particular, of the aeration pipettes as well asthe composting processes and the treatment of certain wastes.

SUMMARY OF THE INVENTION

The purpose of this present invention is to allow the production of a“mature” compost in eight weeks of fermentation and maturation, with noturning in the fermentation and maturation phase, and with no biofilter,in particular for the composting of green waste, biowaste andfermentable waste, and with no production of bad odours.

To this end, the installation of the invention includes an aeration bedthat is composed of at least four aeration lines per fan, with aseparation between the aeration lines of two meters at most, for thecomposting of green waste, biowaste and fermentable waste, with anobligatory covering of the waste in the fermentation and maturationphase of at least twenty to thirty centimeters of purified maturing andrefining compost, by means of a composting process that functionsprincipally by positive ventilation (blowing of air into the heap underpressure, and the absence of vacuum), with a composting process that isorganised in the form of tubular rather than trapezoidal heaps, with aregular separation between the aeration pipettes for distribution of theair, at the level of each (equidistant) aeration line, and therefore aseparation between the aeration pipettes that does not vary regardlessof the distance between the fan and the linear aeration that constitutesthe aeration bed, with a distance between the aeration pipettes of theorder of 20 centimeters.

This present invention has the additional objective of efficientlydealing with heights or depths of waste that are greater than thosehandled up to the present, while also dispensing with any turning duringthe phases known as fermentation and maturation, and of achieving thiswithout the production of bad odours, and therefore with no biofilter.

In this context, the height of the waste to be composted will no longerbe of the order of three meters but even four meters for green waste,biowaste and fermentable waste, and two meters sixty-five for compostedsludges.

The length of each linear aeration arrangement can be at least fortymeters from the composting machinery, which is at least four times fortymeters per fan with a power rating of more than 5 and less than 6 kW,making a total of one hundred and sixty meters of aeration pipes per fanat this level of power.

Parallel to this, whatever the type of waste treated, consideration hasbeen given to the design of tubular aeration pipettes which are in asingle piece, fitted with securing clips, these pipettes being inserteddirectly on the aeration pipes.

Parallel to this, and according to another particular method ofmanufacture of the aeration pipettes, consideration has also been givento the production of a hollow tube directly.

According to one possible embodiment of the aeration pipette, themanufactured pipette includes a clip in its lower part. According to asecond possible method for the design of the aeration pipette, the clipcan include at least one notch or cut or even several notches or severalcuts, in order to further improve the retention of the clip of theaeration pipette in the main air distribution pipe to which the aerationpipettes are clipped.

According to a second possible design method, complementary to the firstmethod of design of the aeration pipette, the latter can also include athread to enable the insertion of a plug of the threaded type, into theupper part of the aeration pipette. It is this solid, threaded plug thatwill then be drilled after formation of the concrete bed. The purpose ofthis thread is to enable the replacement of any traditional pluginserted into, or located within the pipette head.

In the context of the aeration pipette with threading of it upper part,it is intended that the depth of the thread in the pipette head shouldbe exactly equal to the thickness of the threaded plug. The firstsdrilling tests on the threaded plugs showed in fact that when the threadof the aeration pipette has a thread depth that is greater than thethickness of the threaded plug, then during the drilling out of thethreaded plug, the latter is pushed into the pipette head. This pushinginward of the threaded plug then obliges the operator to re-screw andre-position all the aeration plugs that have been pushed into theaeration pipette head, level with the top part of the concrete screed,and this very constraining.

Usually, the bed is formed at the level of the heads of aerationpipettes in order to avoid the clogging problems associated with theprocessing of the waste. In fact, when the plug is positioned level withthe concrete bed, the air pressure is easily able to expel any pieces ofsludge and fine particles clogging the air distribution holes of theaeration pipettes.

Normally, the formation of the concrete over large areas cannot ensurethat all of the pipette heads will be positioned level with the concretescreed. They can therefore be buried several millimeters or even somecentimeters under the concrete. The pipette heads must then be uncoveredso that they can be drilled out. This then creates a space of a fewmillimeters or centimeters forming a volume between the top level of theconcrete screed and the buried aeration pipette head. During theoperation of the platform, this space fills up with sludge or fineparticles, resulting in plugging of the buried aeration pipette head.The aeration pipette then becomes unfit for its purpose. In order toremedy this situation, a new type of threaded plug has been designedthat allows errors due to formation of the concrete to be corrected.

Likewise, for the aeration beds intended for use in the design ofbiofilters, another type of threaded plug has been considered, in whichthe shape of the top part is raised in relation to the concrete screed,and whose shape is more particularly sloped or even rounded or conical,thus avoiding the risk of clogging of the pipettes in the long term,associated with the breakdown over time of the organic biomass.

According one particular method of design of these threaded plugs, theyare manufactured from a threaded rod of greater length that the threadedoriginal plug inserted in the pipette head. The threaded rod is directlycut to the correct height so that the resulting aeration plug will bepositioned level with the concrete screed. This positioning of thethreaded plug eliminates the risk of later clogging. The plug, levelwith the concrete screed, is then drilled to allow distribution of theair. In a second possible method for the design of the threaded plugs,they can include a reaming or hollowing out at the lower end of theplug, of larger diameter than the air distribution hole (in the internalposition of the pipette), thus reducing the thickness of the plug,between the air distribution chamber created for the tube of theaeration pipette and the top part of the plug in contact with the waste.

The purpose of this reduction in the thickness of the plugs is toimprove the effectiveness of the expulsion of any pieces of organicparticles or sludges that may have plugged the holes in the saidaeration pipettes.

In parallel with the above, another innovation has been introduced formonitoring the processing in platforms for the composting and treatmentof waste. This involves installing, on the devices for regulation andmeasurement of the gases, and in particular for measurement of oxygen orany other gas, a filter for trapping of the dampness and of theparticles drawn in by the intake pump of the measurement andair-sampling device. This filter is installed at the level of each ofthe intake pipes of the air drawn into in each heap, at the positionwhere the air is sampled for the said gas measurement. The result ispipes that are clean and free of condensation products, and which arefit for reliable measurement the gases to be analysed.

Again in parallel with the above, it is also planned to install, inaddition to the gas measurement device, a compressor for the productionof compressed air. The purpose of this compressor is to regularly purgethe condensation products present in the pipes used to transport the airdrawn in by the air pump, toward the probes for measurement of the gasesanalysed. The transmission of air in the gas measurement and samplingpipes is controlled by a solenoid valve which is timed or controlled bythe automatic process control system. The compressor can take the placeof filters installed on the pipes for analysis of the gas or gases.

According to one possible method for installation of the wastecomposting or treatment process, which combines the compressor and thetrapping filters (using a number of filters that is determined accordingto the number of heaps in which gas analysis is effected),short-circuiting of the filter installed on the gas sampling or analysispiping is effected using an additional pipe installed as a bypass to thepipe feeding the filter, for each filter installed. Each of theseadditional pipes, installed as bypasses, is equipped with a non-returnvalve, so that the air blown in by the compressor is able to escape andnot be blocked or impeded by the installed filter. This filter isintended to operate in the direction opposite to the direction oftransmission of the air supplied periodically by the compressor. Thecompressor sends the air from the compressor toward the compost heap inorder to purge the pipe of sampling air. On the other hand, the gasmeasurement pump draws in the air coming from each heap, which it drawstoward itself and then transmits to the probes, which it supplies withair. This drawn-in air therefore moves in the reverse direction to thatsent by the compressor.

In parallel with the above, the inventors have also discovered that inthose composting platforms fitted with biofilters, it is possible andmore economic to dispense with the gratings traditionally employed tosupport the biomass, and to replace them with ballast. In this context,the manufacturers of platforms traditionally use very economicalballasts that are composed of crushed and angular stones such as thoseused to limit vibration of the rails during the passage of the trains(the ballast used on railway lines).

The inventors have discovered that it is advantageous to use not aballast of crushed and angular stones but rather special ballastscomposed of cobblestones (meaning ballast composed of stones that arerolled, blunted and of generally rounded shape such as those that areproduced in some fast-running rivers or at the seaside).

In this context, the inventors have discovered that the cobblestonesresult in a better distribution of the air in the biofilter, since theyform a perfectly cellular structure, in contrast to the angular stones.These cobblestones thus provide the right conditions for correctdistribution of the foul air under the biomass. The inventors have alsodemonstrated that this ballast of cobblestones also behaves as theequivalent of the structures that are currently installed withinscrubbing towers.

In fact, the ballasts composed of cobblestones favour the fixing of thebacteria in a manner that is similar to the cellular structures placedin the said scrubbing towers.

Moreover, on contact with the damp air, the ballast of cobblestones alsofavours condensation of the vapour in the said ballast, and converts itto water.

The condensation of the vapour into water limits or even stops thedistribution of these vapours outside the biofilter. It should beremembered in particular that part of the bad odours is located incontact with the water molecules. Part of these bad odours can thereforebe transported by this condensation water which will be trapped and runoff into the ballast of cobblestones rather than escaping to theexterior.

Moreover, if the damp air carried in the cobblestone ballast is acid,then the resulting acid water then flowing in the ballast can also becompared to the equivalent of a conventional scrubbing process of thetype employed in a so-called acid scrubbing tower. The advantage of theballast is then that it improves the treatment of the air and allows animproved reduction of certain malodorous molecules, and in particular inair that is loaded with ammoniac.

The results regarding the purification of the air in biofilters that aremade up using cobblestone ballast are therefore superior to thoseobtained in the case of biofilters constructed with gratings or simplyusing a ballast of the type used for the construction of railway track(ballast of angular stones).

Advantageously, according to another possible method for the design ofthe biofilter with cobblestone ballast, a device for the distribution ofliquids, either of the acids or alkaline type, can also be installedabove the cobblestone ballast, directly between the top part of thecobblestones and the biomass or in the biomass itself, or directly onthe biomass above the biofilter. This device, combined with thecobblestone ballast, then allows distribution of the liquid, whetheracid or alkaline, or combined with a cocktail of enzymes or bacteria,according to the type of air to be treated, and thus improves thereduction of the bad odours.

In addition to the traditional purification function of the biofilter,this device can thus be used to achieve a second purification functionof the air to be purified. The biofilter then behaves as an improvedbiofilter by virtue of the cobblestone ballast. It also behaves like asimplified, though quite functional, scrubbing tower. The biofilter thushas a double purification function, namely original and new.

Other characteristics and advantages of the invention will emerge moreclearly from the description that follows, and which is provided by wayof an unlimited guide, with reference to the appended figures, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in perspective of a compost heap composed of fouraeration lines fed by a fan.

FIG. 2 is an exploded view in section of an aeration pipettemanufactured as a single part.

FIG. 3 is an exploded view in section of a tube to be used in themanufacture of a manufactured aeration pipette.

FIG. 4 is an exploded view in section of an aeration pipette with nothread in its top part but fitted with a clip.

FIG. 5 is a detailed view, exploded and in section, of at least onenotch created in the clip of the aeration pipette.

FIG. 6 is an exploded view in section of an aeration pipette that alsohas a thread in its top part.

FIG. 7 is an exploded view in section and in detail of the top part ofthe pipette head, and of a threaded plug of the same size as the threadin the pipette head.

FIG. 8 presents, in section, a threaded rod for the manufacture ofthreaded plugs, used for correction purposes in the formation of thecompost bed.

FIG. 9 presents, in section, the drawback of a pipette head that hasbecome submerged into the concrete, and the space above it which hasbeen filled in with sludge or fine particles, thus blocking the airdistribution aperture.

FIG. 10 is a view in section of a special threaded plug used to correctthe error in the formation of the bed and to position the top part ofthe plug level with the concrete screed.

FIG. 11 is a view in section of a threaded plug, drilled and reamed outon the inside, to improve the effectiveness of removal of the pieces ofsludge.

FIG. 12 presents a special threaded plug, specially drilled and designedfor the distribution of air in a biofilter-type aeration bed.

FIG. 13 presents this same plug, drilled and with its bottom hollowedout, allowing the risk of clogging of the special biofilter plug to bereduced.

FIGS. 14, 15 and 16 present these same plugs in section, before theyhave been drilled out.

FIG. 17 presents the improvement related to gas measurement using theair sampling rod inserted into the heap, together with the gas samplingpipe, the filter added for trapping the particles and condensationproducts, and the solenoid valve for control and regulation of the gasintake.

FIG. 18 presents the improvement in gas measurement, with theinstallation of a compressor to purge the condensation products, and itssolenoid valve for automatic control of the said purge operation.

FIG. 19 presents a view in section of the device used to short-circuitthe filter for trapping the particles and condensation products, whilealso allowing the escape of the air produced by the compressor. In thisfigure, the non-return valve is installed on the pipe added as a bypass,in order to prevent the air drawn in by the intake pump from passing viathis added pipe so that the air drawn in by the pump would therefore notbe fully processed by the filter.

FIG. 20 presents a view in section of a biofilter in which the base isequipped with cobblestones which are used both as a support for thebiomass and as a structure for the distribution of air under thisbiomass.

FIG. 21 presents a view in section of a biofilter equipped withcobblestones, and with a device for the distribution of liquids orcocktails of bacteria or enzymes, placed between the cobblestones andthe biomass.

DETAILED DESCRIPTION OF THE INVENTION

The descriptions that follow refer to FIGS. 1 to 21, which represent thenew devices and new techniques associated with the composting or thetreatment of waste, according to the different preferred, though notexclusive, embodiments of the invention.

The installation includes an aeration bed (1) composed of one or morefans (2). Each fan (2) performs the distribution of air in the aerationbed (1) via a minimum of four aeration lines (3) per fan (2). Eachaeration line (3) is equipped with main aeration pipes (4) into whichare inserted the aeration pipettes (5) for the distribution of air. Theaeration pipettes (5) are spaced at intervals of about 20 centimeters,all along the main aeration lines (4). The separation between each ofthe main aeration lines (4) is two meters at most. The heaps of waste(6), made up in a tubular (7) and not trapezoidal manner, areprogressively covered during the filling and creation of thefermentation heaps, consisting of twenty to thirty centimeters ofpurified maturation or refining compost (8). The composting process ismonitored by measuring the temperature, and also by measuring the oxygenin the heap. Each main aeration pipe (4) can distribute the air up to adistance of 40 meters, giving a cumulative total length of 160 meters atmost, by means of fans (2). The fan assemblies (2) are of the high powervariety, with a consumed power per fan (2) of between 5 and 6 kW. Theheight of the waste that can be composted can easily reach 4 meters. Theeffectiveness of the aeration system associated with the aeration bed(1) is such that the waste can be composted with no turning during aperiod of eight weeks, during which they are left on the aeration bed(1), during which the process control means that the heap can besupplied continuously with oxygen, and so that the waste remains in anenvironment that is totally aerobic, while never allowing the level ofoxygen measured in the waste to fall below a rate of 8% in comparisonwith the quantity of 21% of oxygen present in the air, this reducedlevel of 8% oxygen being due to the consumption of oxygen by thebacteria present in the waste, in the course of the fermentation and/ormaturation phase. This process allows the production of a mature compost(by reference to the Solvita test) by the end of this eight-week period,compared to the usual twelve weeks. It is a process that requires noturning, is free of odour, and does not require the use of tarpaulins tocover the waste. The main air distribution pipes (4) are a minimum of160 mm in diameter. The bends in the pipes (9) associated with the fans(2) for distribution of the air are of large turning radius, of the 5Dtype, in order to limit the pressure drops. The first manifold (10) fordistribution of the air leaving the fan (2) allows a balanceddistribution of the air, with 50% of the air volume sent to each of thetwo secondary pipes dividing the air between the two secondary manifolds(11). The two secondary air distribution manifolds (11) also effect a50-50 split between the four main aeration pipes (4) for distribution ofthe air under the aeration bed (1). The process concerned preferablyfunctions by blowing under pressure so as to allow maximum aerationeffectiveness to be achieved. The process also functions as a “pressurechamber”, guaranteeing the same pressure and the same quantity of airdistributed at the level of each aeration pipette (5), to each point ofthe compost heap (6). All the parameters associated with breakdown ofthe waste within the heap (6) are thus virtually the same, namely thesame degree of maturation and therefore the same temperature of thecompost produced at any given moment for the similar mixtures of wastemade up into heaps (6).

According to one particular embodiment of the invention represented byFIG. 2, the main aeration pipes (4) can be equipped with aerationpipettes (5) produced as a single part. This single part includes a clip(12) and a plug (13) to provide for the sealing of the aeration pipeduring the formation of the aeration bed (1).

According to this particular embodiment, the aeration pipette (5) can bemass produced by a process involving the injection of plastic materialsin a mould.

According to a second particular embodiment of the aeration pipettes(5), the latter can be manufactured from a simple hollow tube (16), asshown in FIG. 3. This tube (16) should preferably be in a plasticmaterial and easy to work.

The tube (16) can be also be manufactured from other suitable materialssuch as resin or glass fibre though not excluding others. The tube (16)can be processed so as to allow the formation, in its lower part, of aclip (12) as represented in FIG. 4.

According to a variant of implementation of the clip, as represented inFIG. 5, the clip (12) can be equipped with at least one longitudinalnotch or cut (18), allowing better latching of the clip (12) onto themain aeration pipe (4).

According to a variant of implementation of the aeration pipette (5), asrepresented in FIG. 6, the latter can be machined both at its lower partand upper part, so as to allow it to be fitted with both a clip (12) anda thread (14) to allow the later insertion of a threaded plug (15) intoits upper threaded part.

In this context, the thread created (14) will be located inside the tube(16). According to a preferred a embodiment of the invention, asrepresented in FIG. 7, and in order to avoid the unscrewing of thethreaded plug (15) screwed into the top part of the head of the aerationpipette (5), during the drilling out of the threaded plug (15), beforethe platform is brought into service, the thickness of the internalthread (14) of the aeration pipette (5), will be equal to the thicknessof the threaded plug (15) inserted into the head of the aeration pipette(5).

According to a preferred embodiment of the threaded plug (15), thelatter will be manufactured from a solid tube which is then machined forcreation of the internal thread, or even from a full rod which isdirectly threaded and cut to the desired length.

According to one particular embodiment of a special plug (17), asrepresented in FIG. 8, where this plug is used to correct the errorsthat arise during the formation of the aeration bed (1). The specialthreaded plug (17) will then be of a size that is greater than thethickness of the thread (14) created in the head of the aeration pipette(5) so that the new pipette head can be positioned level with theconcrete screed (18), thus eliminating the problem created by cloggingof the pipette heads (19) when the latter have sunk below the concretescreed (18).

According to one particular embodiment of a special plug (20), asrepresented in FIGS. 12 and 13, the purpose of the latter is to effectthe distribution of air under a biofilter, in which the materials areleft in position for a long time. This biofilter is composed of anaeration bed (1) in possible contact with the biomass used forpurification of the air, where the biomass can be in contact with theaeration bed (1) for distribution of the foul air or where the biomasscan be in contact first with a plenum for homogenisation of the air, ofthe grating type with ballast for supporting the biomass on this sameaeration bed. Special threaded plugs (20) are provided, in which theaeration hole (21) will be located above the concrete screed (18)constituting the aeration bed of the biofilter (1), but where the finesorganic particles resulting from the breakdown of the biofilter (24)cannot be deposited and stagnate on the special plug (20).

The top part of the plug, as represented in FIG. 1, will be sloped,rounded or conical in shape (in all cases not horizontal or not incurvedtoward the centre of the pipette), thus avoiding the stagnation of thefine organic particles or of the sludges resulting from the breakdownprocess of the biomass, these particles or sludges (22) being in contactwith the aeration hole (21) of the aeration pipette (5) fitted with thespecial biofilter plug (20).

According to a variant applicable to the creation of all these plugtypes, such as that presented in FIGS. 11 and 12, each threaded plug canbe hollowed out in the lower part of the plugs (25), so as to reduce thethickness of the reamed plug as much as possible, and thus to improvethe effectiveness of the system for expulsion of the fine particles andsludges that can clog the pipette when the fan is brought intooperation.

The thickness of the reamed plug (25) should be at least three or evenfour millimeters so as not to be too fragile, and in order to cope withthe passage of machines over the aeration bed (1).

Regarding sampling of the gases, for their analysis and for monitoringthe composting or waste treatment processes, the installation asrepresented in FIG. 17 includes not only a gas sampling rod (26) foreach compost heap (27), but also, on the pipe for sampling of the gas(28), an additional filter (29) for trapping the condensation productsand the fines organic particles drawn in by the air pump (30) installeddownstream of the probe or probes for measurement and analysis of thegas or gases (31), and of the solenoid valve (32) that controls theintake of the gases to be analysed.

The installation described above, and as represented in FIG. 18,includes a compressor (33) for purging the condensation products. Thecompressor (33) will be controlled by a solenoid valve (34) which istimed or in turn controlled by the automatic processor controlling theprocess (35), and separate from the solenoid valve (32) controlling theintake of the gases.

The compressor (33) will preferably be installed upstream of the airpump (30) and downstream of the solenoid valves (34) used to control theintake of the gases, in such a manner that it is also able to clean thelatter because of the cleaning effect of the compressed air injectedinto the pipe used to sample the gases analysed (28).

It goes without saying that the installation, as represented in FIG. 18,can include both a compressor (33) and a filter (29) for the trapping ofparticles.

In this context, the installation is then equipped with an additionalpipe (36) used to short-circuit the filter (29) when the compressor (33)is operating. This pipe (36) is also equipped with a non-return valve(37), forcing the air drawn in by the pump (30) for sampling of gases tobe analysed to pass via the filter for trapping of the condensationproducts (29).

The composting installation can then also be equipped with biofilters(34), as presented in FIG. 20, composed in the lower part and acting assupport for the biomass (38), made of cobblestone ballast (39).

In a variant, the biofilter (34) can be equipped, between thecobblestone ballast (39) and the biomass (38), with a device for thedistribution of acid or alkaline liquids (40), or of enzyme or bacteriacocktails.

It goes without saying that the liquid distribution device (37) can beplaced directly between the cobblestone ballast (39) and the biomass(38) or even within the biomass or on the latter. The improved biofilter(34) will therefore have a purification function of the scrubbing towertype, in addition to its biofilter function.

The device for the distribution of the liquid or liquids (40) or of thecocktails of enzymes or bacteria, can be of the sprinkler-bar type,though not exclusively so. It goes without saying that all theseinnovations can be used individually or in combination in the compostingprocesses or for the elimination of pollution and the treatment ofwaste.

1. A device for biofiltration, purification and treatment of aircomprising: an aeration bed for the distribution of air and forcollection of the process liquids (1) on which is placed-a cellularstructure resting-directly on the aeration bed, characterized in thatthe cellular structure comprises stones of generally rounded shape; anda biomass disposed on the cellular structure.
 2. A device according toclaim 1, characterized in that the cellular structurecomprises-cobblestones resting directly on the aeration bed.
 3. A deviceaccording to claim 2, further comprising one or more devices for thedistribution of liquids.
 4. A device according to claim 3, wherein theone or more devices for distribution of liquids are located on thebiomass and/or in the biomass and/or between the biomass and thecellular structure.
 5. A device according to claim 4, wherein theliquids are selected from the group consisting of an acidic liquid, abasic liquid, a liquid comprising at least one enzyme, and a liquidcomprising at least one bacteria.
 6. A device according to claim 4,wherein the one or more devices for distribution of liquids is asprinkler bar.
 7. A device according to claim 3, further comprising aliquid disposed in the cellular structure.
 8. A device according toclaim 3, wherein the liquids are acidic.
 9. A process for biofiltrationof foul air produced in a composting process, comprising: causing theair to contact the cellular structure of a device according to claim 4,wherein the cellular structure acts as a scrubbing tower.
 10. A processaccording to claim 9, comprising: dispensing one or more liquids from adevice for distribution of liquids.